1. Field of the Invention
The present invention relates to nuclear plants and more particularly to a nuclear reactor protection system and a self-test system. Specifically, a universal logic card is disclosed which is capable of placement in any number of channels within such a nuclear reactor protection system. For example, between sensors such as core overheat sensors and a corresponding safety or operation function, such as the insertion of Boron to shutdown a reactor, there is located the universal logic card of this invention with pre-programmable digital logic contained thereon conformed to the particular channel in which the card is inserted. The card, pre-programmed to conform to the channel logic, executes the necessary channel logic to activate the protection system, responds to system-wide test using short duration pulses transparent to the actual operating system; and, executes self-test continually in the absence of either an actual system exercise or the generic tests under the system controller.
This invention relates to a self-test subsystem for nuclear reaction protection system. The applicant hereby incorporates by reference U.S. patent application Ser. No. 402,053, filed July 27, 1982, by Hill et al and assigned to the same assignee herein.
Nuclear protection systems include electronic controls, typically embodied in a discrete digital and analog format within circuit cards. These circuit cards are located intermediate between devices such as sensors (as for detecting core overheat) and controls (as for providing Boron injection to shutdown a reactor). In the referenced application, constant surveillance of the nuclear system protection system is provided by a system controller microprocessor. This system controller microprocessor serially addresses protection system circuit cards and loads them at predetermined input points with test commands. The addressed cards are thereafter simultaneously activated by system wide command. A test pulse is emitted which pulse is so short in duration that its effect is transparent to the reactor protection system and therefore cannot cause overall reactor protection system operation.
The transparent pulses, however, pass through the actual actuating electrical components of the cards to verify along the real actuating path the operating integrity of the system. After enduring an appropriate response interval, the output state of the system is recorded in system-wide resident registers. Thereafter, with the response data contained in these registers frozen at the recorded state, the output is read by a monitoring computer, typically the system controller microprocessor. This result is compared with the expectant output already contained in computer memory. If the correspondence between the memory output and the register output is found, the next sequential set of test commands is acted upon. If correspondence is not found, a sub-routine search is automatically conducted to locate the error. A protocol of redundancy even within the test system is disclosed in the incorporated by reference patent application.
2. Description of the Prior Art
In the system disclosed heretofore, each channel within the the nuclear power plant and the nuclear reactor protection system itself had to be discretely wired with discrete logic elements such as primitive gates and "relay trees". Volumes of up to hundreds of such cards were maintained in inventory for the many channels throughout a nuclear protection system. The costs of maintaining such are on site card inventory are high and the construction of numerous discrete hardwired logic circuits is unnecessarily as well as expensive to manufacture.
Placing logic circuitry in software is well known. However, placement of digital logic in software for essential functions in reactor protection system operating channels has heretofore not been utilized. In short, software logic, has been ruled out as a candidate to substitute for discrete digital circuitry because of inability to verify correct operation of the software.